Thermostatic circuit closer



Sept. 8, 1931. G. H. BRADY THERMOSTATIC CIRCUIT CLOSER Filed Feb. 18, 1929 i I a mum:

I g'rvue'nl oa Geaye Efiray.

Patented Sept. 8, 1931 UNITED. STATES PATENT OFIFICE GEORGE H. BRADY, OF BALTIMORE, 'MABYLAND, ASSIGNOR TO IMPROVED FIRE IDE- TECTOR CORPORATION, OF

BALTIMORE,

THEBMOSTATIC CIRCUIT CLOSER Application filed February 18, 1929. Serial No. 340,892.

This invention relates to thermostatic circuit closers for fire alarm systems, and particularly to circuit closers of that general type disclosed in my prior application filed June 7, 1928, Serial No. 283,67 5.

One object of the invention is to provide a construction whereby the metallic casing of the device will be so disposed. as to properly space all current carrying parts from a ceil- 19 ing or other surface on which the device is mounted, and whereby also the current carry- "ing parts are properly spaced from each other and insulated from the casing to obviate all liability of short circuits, sparking or other deleterious actions, as well as liability of cur- ,in which all the current carrying parts are mounted upon a common support so as to. be easily and conveniently applied to or removed from the casing, and in which the device when mounted in position for use is protected against dust accumulation or deposits of paint'or the like when a building in which the device is installed is being redecorated;

and in which, further, simple, reliable and eflicient means are provided for fastening the conductor wires to the terminals against casual loosening or disengagement.

The invention consists of the features of construction, combination and arrangement of parts, hereinafter fully described and claimed, reference being had to the accompanying drawings, in which v Figure 1 is 'aperspective view of my improved circuit closer:

' Figure 2 is a face view thereof with a portion ofthe'cover plate broken away.

Figure 3 is a central longitudinal section through the device. n i V Figure 4 is a cross-section on the line 4-4 of 'Figure 3, showing the contact screw as applied for adjustment and before its outer end is cut off.

Figure 5 is a similar view showing the contact screw 'in final adjustment and 1ts outer end out off.

Figure 6 is a view of the blank from which the cover plate is made.

Figure 7 is a detail section through one of the binding posts. r

In carrying my invention into practice, I provide a thermostatic circuit closer comprising a casing of oblong rectangular form in plan and of rectangular form in cross-section, said casing consisting of a channeled body 1, formed of sheet metal, and having a back'wall 2 and side walls 3, the casing body being normally open at its endsand front side. As shown, the walls 3 are provided with flanges 4 bent inwardly towards each other at the front side of the casing body for the purpose of reducing the width of the front opening and retalning in position a cover plate or front wall member 5. The cover plate is also made of sheet metal from a blank of the initial form shown in Figure 6. This cover plate comprises a body portion which is preferably transversely arched and closes the opening between the flanges 4, said cover plate being overhung at its lateral edges by said flanges so asto be retained from outward displacement. The cover plate is provided with angularly bent portions 6 terminating in right angularly bent perforated attaching projections or cars 7, whereby the circuit closer may be fastened at the point of use to the ceiling of a room or any other suitable support. a The body part of the cover plate is preferably provided throughout with perforations 8 for a purpose hereinafter described.

Oneof the sides, that is, either the side 3 or the side 4 of the casing body, theside 3 in the present instance, is provided with a pair of spaced longitudinal slots 9 separated by an intermediate portion or bridge piece 10.. On this side of the casing is mount-- .ed an insulating support 11 for the current carrying parts of the device. This support comprises an oblong rectangular block or strip of bakelite, or other similar material screws 18 and 19. These screws 17 and 19,

the former of which passes through the strip 11 and the plate 13 and the latter of which passes through the block 15, strip 11 and plate 14, provide binding washers 20 and binding nuts 21.

The screw 16 has a conical or pointed inner end 22 projecting beyond the strip 11 and through one of the slots 9 into the casing, said conical end of the screw providing a preliminarily adjustable but normally fixed circuit closing contact. Arranged within the casing for coaction therewith is a bi-metallic strip 23 composed of two metals of different coelliciencies of expansion and contraction. These metal strip members are coextensive in length and welded together and are jointly secured at one end by the screws 18 and 19 to the block 15. The metals of the strip 23 are preferably of non-corrosive material, or they may be provided with a coating of noncorrosive material or adapted to protect the same from corrosion. The screw 16 is provided with fine or micrometer screw threads, the threaded portion of said screw engaging threaded openings in the strip 11 and plate 13. "initially the opposite or outer end of the screw 16 projects, as shown in Figure 41, a suitable distance beyond the outer face of the plate 13 and is provided with a niclr or other means 24; whereby a screw-driver or other suitable tool may be engaged therewith to secure it into position. The screw is preferably made of soft metal, so that after having once been set or adjusted its outer end or projecting portion may be cut oli flush with the outer face of the plate 13, so as to prevent accidental displacement of the contact screw 16 from its set position or of meddlesome persons turning it and changing its position. The pointed end22 of the screw 16 lies in the path of movement of the free end of the strip 23, when the latter is bowed or deflected in one direction by the action of heat at a certain predetermined temperature, and the pointed form of the contact and wiping motion of the strip over the same reduces to a material extent liability of the collection of dust or other foreign substances causing imperfect contact, the contact surfaces being -ept clean, so that a reliable contact will always be made. Fastening screws 25 are provided for screwing the strip 11 at its ends to the ends of the casing wall 3, and a fastening screw 26 is provided center recas of the strip 11 for fastening it to the bridge piece 10. Instead of employing the screws 25 and 26, bolts and nuts may be used in lieu thereof.

It will be observed that all the current carrying connections, above-mentioned, are of unitary construction, that is to say, are mounted upon a common insulating support llwhich is detachably secured to the wall 3 of the casing and which provides for the mounting of all the current carrying connections upon, or the dismounting of said current carrying connections from, thecasing in a simple and convenient manner, and that when the parts are assembled all of the current carrying parts are insulated from the casing. In the device as organized for use the contact pin 16 and head of the binding post 1? lie within one of the slots 9 free from connection with the casing, while the block 15 projects through the other slot 9. 111 applying the unitary current carrying structure to the casing body, the current carrying structure is brought into position at the side 3 so that the free end of the strip will be in alineinent with the slot 9 to be occupied by the block 15, whereupon such end of the strip 23 is inserted into the casing body through said slot and the current carrying unit then moved longitudinally in the direction toward the other slot until the block 15 comes opposite the slot through which the strip 23 has been introduced, after which the current carrying unit is simply moved inward to bring the parts thereof in work ing position and scoured in place by means of the screws and 26. When it is desired to remove the current carrying unit all that is necessary is to unfasten the screws and 26 and to shift the unit longitudinally in the reverse direction to that in which it was introduced and then to withdraw it laterally, as will be readily understood. l/Vhen the device is disposed in use, as upon the ceiling of a room, to which it is attached, by the ears 7, the body of the casing will be spaced a proper distance from the ceiling to allow heated air to circulate completely around the device, and to dispose the binding posts at a safe distance from the ceiling, and so as to allow them to be more conveniently reached when required, while the perforated front wall or cover plate will face down wardly so that the heated air from below will flow into the casing and be confined for a period, thus, in case of a conflagration, providing for the more certain exposure of the thermostatic circuit closer 23 to the rising heated currents of air. At the same time such arrangement of the parts will insulate all the current carrying parts, not only from the wall and adjacent surfaces, but also from the casing of the device, oliiviating liability of short circuits or current leakages or of shocks being transmitted to persons who may accidentally touch the casing or bring tools in contact therewith. When the parts are arranged in the manner stated the thermostatic circuit closer 23 will be disposed edgewise in a Vertical position and thus better protected against the deposit of dust thereon, so that by such arrangement and the wiping action previously described, a circuit contact and circuit closing engagement between the surfaces 22 and 23 will occur, to sound the alarm, when the strip 23 is bowed at a predetermined degree'of heat.

The washers 20 and binding nuts 21 are of special construction in order to secure a firm clamping engagement of the ends of the circuit conductors 27 and. 28 therewith. As shown particularly in Figure 7 each washer 20 comprises a conical body, the 'top wall of which is provided with a conical portion 29 depending within the body con'- centric therewith and having at its apex the opening for the passage of the binding post, and the nut 21 has a projecting portion 30 which is longitudinally tapered and adapted to enter the conical part 29 of the washer. In applying awire, the end of the wire is looped and engaged with the binding post and the nut then threaded in position to engage the looped end of the wire. As the nut is threaded on the binding post, its portion 30 forces the looped end of the wire down into the conical portion 29, which crowds it into the binding contact between the same and the nut, and the pressure of the nut on the conical Washer diametrically stresses said washer so as to put .it under tension, with the result that the washer securely grips the binding poit, the wire and the binding nut, thereby tightly uniting the partsagainst any possibility of relative movement oruntil the nut is forcibly reversely turned to relieve the binding action.

Having thus fully I claim':

1. A circuit closer embodying a casing having a slotted wall, a bimetallic circuit closing strip disposed upon the interior of the casing, a pair of binding posts one of which is connected to one end of the strip, a contactadapted to be engaged by the other end of the strip to close a circuit including the same and the binding posts, the said bindingpostsibeing arranged exteriorly of the casing and'the first-named post and contact extending through the slotted wall of the casing, and an insulating support on the exdescribed my invention,

. terior of the casing carrying the circuit clos- 2. A circuit closer ing stripfbinding posts and contact and forming with said posts a thermostatic switch unitarily applicable to and removable from the casing. embodying a casing having, means at one side thereof for attaching said casing to a surface and spacing the same therefrom, thermostatic circuit closing elements within the casing, binding posts connected therewith and disposed without the casing, and an insulating support for said elements and binding posts mounting the same at a side of the casing at right angles to the side thereof first-named, said support forming with said elements and posts 2. current carrying means unitarily applicable to and removable from the casing.

'3. A circuit closer embodying a casing of angular form in cross-section having means named and supporting the thermostatic strip and binding posts respectively within and without the casing; j I

4. A circuit closer comprising a casing having a wall provided with a pair of spaced longitudinal slots and an intervening bridge piece an insulating strip arranged outside said wall, a contact carried by said strip and projecting through one of said slots into the casing, an insulating support carried by said strip and projecting through the other slot into the casing, a thermostatic circuit closin strip attached at one end to the latter-name support and having its free end arranged for coaction with said contact, binding osts mounted upon the strip externally o the casing, and means for detachably connecting said strip to the casing.

5. A circuit closer comprising a casing having one of its walls provided with a pan of slots and an intervening bridge piece, an insulating supportingstrip arranged outside the casing and in contact with said wall, terminal plates carried by said strip, a contact engaging one of said terminalplates and projecting through one of the walls into the casing, an insulating support carried by the strip and projecting through the other slot into the casing, a thermostatic strip fixed at one end to said support and having its free end arranged for coaction with the contact,

binding posts connected with the terminalplates, and binding means carried thereby for connecting conductors thereto.

46. A circuit closer embodying a casing having one of its walls provided with a pair of spaced slots and a bridge piece between the same, an insulating supporting strip arranged on the outer side of said wall, terminal plates carried by said strip, binding posts connected with the terminal plates, a contact connected with one of the terminal plates and projecting thrcugh one 0% the slots into the casing, an insulating support carried by the strip and projecting thrcugh the other slot into the casing, a thermcstatic circuit closing strip connected at one end to said support and having its free end arranged to engage the contact, conical resilient Washers about the binding posts and engaging the terminal plates, and clamping nuts on the binding posts for coaction with said Washers.

In testimony whereof I afix my signature.

GEGRGE H. BRADY. 

